leptos-rs/leptos · error

{location:?} expected context of type {type_name:?} to be pr

Error message

{location:?} expected context of type {type_name:?} to be present

What it means

expect_context<T>() panics when no context value of type T has been provided by any owner in the current reactive ownership tree. Leptos context is provided with provide_context and consumed via use_context/expect_context; use_context returns Option, while expect_context is the assertive variant that assumes the context must exist. This panic means the consumer is running outside the subtree (or owner) where that context was provided.

Source

Thrown at reactive_graph/src/owner/context.rs:306

///         let value = use_context::<String>()
///             .expect("could not find String in context");
///         assert_eq!(value, "foo");
///         let value2 = use_context::<String>()
///             .expect("could not find String in context");
///         assert_eq!(value2, "foo");
///     });
/// });
/// # });
/// ```
/// ## Panics
/// Panics if a context of this type is not found in the current reactive
/// owner or its ancestors.
#[track_caller]
pub fn expect_context<T: Clone + 'static>() -> T {
    let location = std::panic::Location::caller();

    use_context().unwrap_or_else(|| {
        panic!(
            "{:?} expected context of type {:?} to be present",
            location,
            std::any::type_name::<T>()
        )
    })
}

/// Extracts a context value of type `T` from the reactive system, and takes ownership,
/// removing it from the context system.
///
/// This traverses the reactive ownership graph, beginning from the current reactive
/// [`Owner`] and iterating through its parents, if any. When the value is found, it is removed,
/// and is not available to any other [`use_context`] or [`take_context`] calls.
///
/// If the value is `Clone`, use [`use_context`] instead.
///
/// The context value should have been provided elsewhere using
/// [`provide_context`](provide_context).

View on GitHub (pinned to 32d20f6c9d)

Solutions

1. Wrap the consuming component (or the whole app) in the provider that calls provide_context for the required type (e.g. QueryClientProvider for QuerySignal).
2. Replace expect_context with use_context::<T>() and handle the None case gracefully instead of panicking.
3. If used in a spawned task, ensure it inherits the correct Owner via Owner::with_current or provide the context explicitly in the task.
4. Check that the provider is not behind a conditional (cfg, Suspense fallback, route guard) that can render before it exists.

Example fix

// before
#[component]
fn App() -> impl IntoView {
    view! { <Todos/> } // Todos calls query_signal -> panics: no QueryClient context
}

// after
#[component]
fn App() -> impl IntoView {
    view! {
        <QueryClientProvider client=QueryClient::new()>
            <Todos/>
        </QueryClientProvider>
    }
}

if let Some(client) = use_context::<QueryClient>() { /* proceed */ } else { // render default or log before calling expect_context }

fn has_context<T: Clone + 'static>() -> bool { use_context::<T>().is_some() }

When it happens

Trigger: Calling expect_context::<T>() (directly or indirectly via query_signal_with_options) in a component, signal getter, or closure whose owner was not created inside a component that called provide_context::<T>() — e.g. calling it before the provider mounts, in a root that is not nested under the provider, or in an async task spawned with the wrong Owner.

Common situations: Using QuerySignal (leptos_query) at the app root without wrapping the app in the query client provider; rendering a component both inside and outside the provider (e.g. in a portal or router fallback); spawning a task with tokio::spawn instead of spawn_local, losing the owner; hydration mismatch where the provider is conditionally rendered.

Related errors

• Tried to access a reactive value that has already been dispo
• at {location}, the `sandboxed-arenas` feature is active, but
• could not find key for index {index:?} at {caller}
• <FlatRoutes> should not be used with nested routes.
• At {caller}, you call `to_server_error()` or use `server_fn_

AI-assisted analysis of leptos-rs/leptos@32d20f6c9d (2026-09-01). Data as JSON: /api/errors/605f0374e6972c7c. Report an issue: GitHub.